A precise move, forcing White to weaken the e3-square.
15. d2g5 After another mistake, White has no chance of saving the game. 15... d8g5 Interestingly, all of this had already been played in a high-level game. 16. a8a7  16... a6b4  17. e1d1 A sad necessity: there's no other way to defend the pawn.